


Don't

by kurtcobains



Category: Life with Derek
Genre: Angst, F/M, Fluff, Romance, Smut
Language: English
Status: In-Progress
Published: 2016-12-12
Updated: 2016-12-11
Packaged: 2018-09-08 01:39:08
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,211
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/8825122
Author URL: https://archiveofourown.org/users/kurtcobains/pseuds/kurtcobains
Summary: Casey and Derek weren't thrilled about being step-siblings. In fact, Casey hardly recognized Derek as a step-brother but more of a nuisance that happened to live in the same environment as her. However, their relationship begins to change when Casey meets a new boy and Derek gets a little jealous.





	

**Author's Note:**

> DISCLAIMER: I don't support IRL step-cest or incest, it's just a fanfic. Enjoy.

Casey McDonald, and her best friend, Emily Davis, walked to their shared locker. Emily was droning on and on about how hot Derek was and how badly she wanted to go out with him. Casey's relationship with Derek, her step-brother, was slightly complicated. Anytime the two of them were near each other, arguing and madness insued. "If you want to date Derek, why don't you just ask him out? It's the 21st century, after all. You don't need him to make the first move." Emily rubbed the back of her neck uncomfortably. "The only time he talks to me is to find out what you're doing, Case." Casey was taken aback by this comment; why would Derek ask Emily about her? She quickly brushed it off. "Gaining information to torture me with in the future, no doubt." She finally replied, looking down the hall for an excuse to change the subject. Her prayers were answered almost immediately. 

"Who's that?" Casey asked, eyeing a spectacularly beautiful male specimen whom she had never seen before. "That's some new kid from America, he's supposed to be like, a really big deal. I heard he came from California. How totally crazy, right?" Casey nodded absently, she really just wanted to talk to this new boy. "I'm going to ask him if he needs a tour around campus or something." Emily giggled and patted Casey's sweater-clad shoulder. "Go get 'em, tiger." She encouraged. Casey's feet began to meet the tile floor, accelerating her to a possible new love interest for herself. As she approached the finish line, she was interrupted be a gleaming Derek, much to her annoyance. "What do you want, Derek? I'm in the process of meeting my future boyfriend." Derek's face twisted as she said that. "Who? That prick from Los Angeles? He's out of it. Probably a big-headed stoner or something." Casey's eyes rolled to the back of her head. "What's the matter with you? Just move out my way, pea-brain." She said the last part of the sentence very slowly, as if he were too dumb to comprehend. "Whatever, I doubt he'll want to go out with somebody as bloody boring as you anyway." Derek turned harshly and walked away. Casey ignored what Derek said and continued on her path. Absent-mindedly, she bumped into the boy, his books flying everywhere. "Oh, I'm sorry!" She gasped, frantically trying to scoop up his books. 

"Don't worry about it," he replied softly, taking the books and caressing her hands slightly. "What's your name?" Casey asked, getting straight to the point. His hands against hers energized her in a way she hasn't felt since… Max. The name stung her mind, as she quickly hid the feelings away again. "I'm Jared Regnet, who are you?" She smiled and held out her hand for a handshake. "The name's Casey McDonald. Do you want a tour of the school? I can help you get to your classes, if you want…" Her voice trailed off as she tried reading his facial expression. "That'd be reall-" he was cut off by a painfully familiar voice, one she loathed wholeheartedly. "I'll show him around, Case. You don't want to be late to your classes, do you?" She began to get very agitated; why was he trying to ruin her chances of getting over Max? "No, that's okay. I can miss a few classes for such a good cause." She thought if she blatantly flirted with Jared, Derek would get the hint and go away. To her dismay, Derek never relented. "I insist, truly. You go ahead, Case. I'll take over from here." Casey huffed and walked away. Derek was so unbelievably annoying! She couldn't understand why he had to ruin her life so incessantly! 

When Casey got home from school that day, she was out for blood. If Derek even dared to cross her path she would lose it and no one would be safe from the line of fire. "Hi, Casey, how was school today?" George called from the kitchen. "Oh, dandy. Just absolutely fantastic." The sarcasm went over his head because he responded with a very happy, "good". She marched upstairs and slammed her door. She was fuming; how could Derek do that to her! Not only was it embarrassing, but it was such a vibe killer. Jared probably wanted nothing to do with her now. An over-protective step-brother in the way? What guy would want to deal with that? She found herself drifting off to sleep, angrily. A soft knock on her door jolted her to an upright sitting position on her bed. She heard heavy breathing on the other side, and chose to ignore it. Figuring it was most likely Derek coming in to gloat. She laid back down on her mattress and stared at the glow-in-the-dark stars that were splattered across the ceiling. George didn't know what Casey would like, so he assumed the stars were a safe bet. She liked them, though. They were a little childish, but she enjoyed looking at stars and it felt like she was looking at the real deal at night. Her mind drifted to Derek again and she just couldn't shake off his behavior; it wasn't entirely out of the ordinary for him. He did that sort of thing constantly, but this time it just felt different. She tried to think of something else, but her mind never faltered away from Derek. 

Eventually, Casey's mother, Nora, called her down for dinner. She trudged down the stairs, still visibly irritated by the events of the day. Derek was sitting at the table, his head turning ever so slightly at Casey entering the general vicinity of the dining room. She decided to switch seats with Lizzie, her little sister, so she didn't have to sit right in front of him. She didn't even want to see his face; she was so mad. George and Nora both sensed something was off, so they treaded very lightly at dinner. Careful not to disrupt the tension-filled, but silent, dinner they were having. George decided he would just tell one of his classic work stories where everyone at the table felt inclined to laugh just so he wouldn't feel stupid. Though his stories were usually exactly that. Derek's gaze fixed on Casey; he was wondering when she would yell at him. He knew that he really pushed her buttons today; so much so that she'll explode in a boisterous matter. Maybe, he decided, he would poke the bear a little bit.

"Casey, how was school today?" He asked with a smirk. Casey glared at him and stabbed the chicken on her plate so forcefully that she nearly broke it. Nora and George exchanged worried looks, knowing just how bad this fight would end up being. "So, uh, Lizzie, how was soccer practice?" Nora said quickly, hoping to keep the peace just awhile longer. "It was so great! I scored nearly five goals today!" Derek smiled. "And Casey scored none, right Case?" That was it; that was what finally broke the peace. "Shut up, Derek! I can't believe you did that to me today! I don't know why you always feel the need to ruin my life, but for once I wish you'd just back off! Out of all the low and selfish things you've done to me, this has got to be the worst! You completely embarrassed me today and ruined a possible chance of finally getting over Max. You don't understand much I needed to get over him and you blew it. So, thanks. I'm glad this is all such a gigantic joke to you. This is my love life, stop meddling in it. Leave me alone and don't dare cross my path again." She pushed her chair back so harshly, that when she got up, it completely fell over. She stormed up the stairs, her footsteps ringing throughout the house. She slammed her door, again, and slid down the back of it. Tears were stinging her eyes but she didn't want to cry; she didn't want Derek to win. She was so tired of him messing everything up for her. 

Derek wasn't expecting the amount of hurt that came across in her voice and if he were being honest with himself, which he rarely is, he would say that he felt a little guilty. "You know, Derek, you should really be nicer to your sister." George said, emphasizing the word "sister". Sister? Casey wasn't his sister. Casey was… His little pet. No, not like that. She was his experiment. No, not that either. What was she? Derek didn't know exactly what their relationship was -- but she was definitely NOT his sister! Marti's his sister. Casey? No way! "I don't really see that happening, do you?" George sighed, and Nora glared at him. Nora's always on Casey's side no matter what and Derek resented that. "Go upstairs and talk to her right now, son. That was inappropriate. I don't know the exacts of what happened but I know that you caused it and it's really messing with Case. You got to fix it." Derek groaned and got up, he wasn't annoyed about going up there, he was scared but he'd never admit that out loud. He walked the stairs feeling ashamed, not because he ruined dinner… again, but because Casey was really mad at him. So much so that he didn't know if he could just fix it by talking it out like most of the other stuff. He got to her door and sighed, trying to bring up the courage to knock. She wouldn't be happy and he knew that and that's what scared him the most. Seeing her so devastated; tear stained cheeks, red nose, snot everywhere. He didn't like thinking about her like that.

He knocked softly, hoping that Casey would answer just so he could make it right. He felt so unnatural. They fought all the time, but this time felt more intense to him. Casey opened the door, she was wearing a tank-top and short shorts and Derek's eyes lingered on every visible part of her body. He immediately snapped back into reality. "Case, can I come in? I just want to talk." Casey smiled, and Derek was shocked. "Why are you so happy, princess? Just ten minutes ago you were on the verge of tears." She flopped down on her bed, her shorts rising up allowing Derek to see the outline of her underwear. He tried not to stare but for some reason, he couldn't help himself. What was going on? Why was everything so weird? "I got a call from Jared and he told me that he wants to take me out this weekend. I'm so glad you didn't ruin my shot for real happiness." He felt hurt. He felt hurt because she wasn't supposed to be with this Jared guy, she was supposed to be with… Who? Who was she supposed to be with? Why did it matter to him? "Oh, well, I guess he didn't get the memo." He said, half out loud, half under his breath. "What do you mean?" Casey's voice raised a little, meaning she was about to flip out on him again. "I told him to stay away from you because you had a boyfriend. I guess he's a home-wrecker." She was so annoyed with him, but she decided not to give into his act. "Except he's not because I don't have a boyfriend. I'm glad you didn't phase him or scare him off. I just have a feeling that this relationship is going to be really important." Derek looked at his hands, he was defeated. He didn't know why he was so hurt and upset. Casey was his step-sister who he loved to torment and that was it. Right? "Well, I just came in to say that I'm sorry. I'll go now." Derek got up and stared at Casey one more time, just to see if she would say anything. She didn't; she sat on her bed reading a book. She didn't even look up when he turned the doorknob. 

As soon as the door shut behind him, Casey jumped up. She realized a lot of things when he was in there: 1.) he sounded jealous (of who? Jared?), 2.) he was staring at her, like, really staring, 3.) he was upset about the whole situation, 4.) he looked back when he left, and 5.) he tried to make Jared not date her. It was so weird; why was he acting that way? Her feelings towards Derek were all over the place and she had no idea where they stood. Are they pals? Are they rivals? Are they siblings? Or… something else? She just hoped that whatever it was, it wouldn't get in the way of her new possible relationship. Even if Jared is just a rebound, she needs it. Derek was in his room thinking about the same sort of things she was thinking about, only he was trying to decide what his true feelings for Casey was. The only thing he knew for sure was she absolutely could not go on a date with Jared and he would do whatever it took to make sure it wouldn't happen.


End file.
